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DTC code PO400 could be caused by a clogged EGR valve or EGR tube. try cleaning the EGR valve, tube
DTC code PO171 is fuel system too lean bank 1
DTC code PO174 is fuel system too lean Bank 2
Most likely suspects are O2 sensors, But can be caused by vacuum leaks and also can be Mass airflow sensor (MAF) try cleaning with electrical parts cleaner
DTC code PO 302 is a misfire at cylinder # 2
Check spark plugs and wires
Try cleaning the EGR Valve first along with changing the spark plug first, and see if any codes erase, in other words start with the cheaper fixes first, as some problems can be causing the other other codes
code p0128 indicates a mechanical fault ( could be the thermostat stuck open)
code p0174 -system too lean -bank2 ===causes --intake /exhaust leak--fuel pressure/pump--injectors--AIR system--hose connection/s
code po171 refers to system too lean bank 1 same as po174 with the HO2S sensor being the culprit. As to all being related . only by way of the o2 sensors
code p0442 is not connected to the first 3 as it is in a different section of the fuel system
Intake or vacum leak will be the first codes 174,171, try idle and spray propane around intake if car idles up, then intake is leaking, otherwise could be a broken vacum line, check with a gauge
P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure
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